Technical Field
The present disclosure relates to a microelectromechanical sensing structure for a pressure sensor, which includes a test structure that is at least in part deformable.
Description of the Related Art
As is known, there are today available pressure sensors such as, for example, the so-called sensors of the MEMS (microelectromechanical systems) type.
Each MEMS pressure sensor comprises a sensitive structure of a MEMS type and a reading electronics.
The sensitive structure, which is also known as “sensing structure”, typically forms a cavity delimited in part by a membrane and is designed to generate an electrical quantity (for example, a capacitive or resistive variation) indicating a pressure. Instead, the reading electronics are designed to carry out appropriate operations of processing of this electrical quantity for supplying an electrical output signal, whether analog (for example, a voltage) or digital. The electrical output signal is then made available, possibly after prior further processing by an electronic interface circuit, to an external electronic system, such as for example the microcontroller of an electronic apparatus that incorporates the pressure sensor.
In greater detail, typically the sensing structure comprises two or more piezoresistive elements, which are arranged in the proximity of the membrane. In this way, the piezoresistive elements undergo deformation following upon deformation of the membrane, and thus modify their own values of resistance as a function of the deformation of the membrane, and consequently of the pressure exerted on the membrane itself.
Given this, there is particularly felt the need to be able to effectively test the aforementioned sensing structures. In this connection, automatic test equipment (ATE) is known, which is designed to test a number of sensing structures, provided, for example, in a same wafer of semiconductor material. For instance, some test systems envisage exerting forces on the membrane, thus from above the wafer, or else applying a pressure from beneath the wafer. Again, other systems envisage arranging the sensing structure in an environment the pressure of which may be varied in a controlled way. Purely by way of example, U.S. Pat. No. 4,708,012 describes a test system that enables exertion of a pressure on a diaphragm for simulating the presence of a desired pressure, and determination of whether the corresponding electrical output signal assumes correct values. In general, the test systems so far known enable effective testing of sensing structures of a known type; however, according to the cases, they may be characterized by a reduced capacity to parallelize the test, or else by high costs.